Cut peppers in half lengthwise and remove seeds. In a dutch oven, cook peppers in boiling water for 3-5 minutes. Drain and rinse in cold water; invert onto paper towels.

In a large skillet, cook beef and onion over medium heat until meat is no longer pink. Stir in the tomatoes, spinach, orzo, oregano, garlic and pepper. Bring to a boil. Reduce heat; cover and simmer for 5-7 mintues or until orzo is tender.

Spoon into peppers. Place in an 11 x 7 in baking dish coated with cooking spray. Cover and bake at 350°F for 30-35 or until peppers are tender.

Sprinkle with cheese; bake 5 minutes longer or until cheese is softened.